The present invention relates to a system for controlling an aperture of a lens attached to a camera. More specifically, the present invention is related to the control of an aperture of a lens which is attached to a camera through an adapter ring.
Generally, when a conventional single lens reflex (SLR) camera has a detachable lens mounted thereon, an aperture control mechanism of the camera is coupled to an aperture control lever of the lens. A spring force is applied to the aperture control lever of the lens, such that when the lens is detached from the camera, the aperture of the lens is either a maximum or minimum size, depending on where the spring force is applied.
Recently lens adapters have been provided such that lenses designed for cameras having a particular size of lens mount can be mounted on cameras having a different size of lens mount. For example, lenses designed to be used with cameras using Brownie film having an exposure frame size greater than a standard 35 mm camera (e.g., exposure frame size of 4.5 cm by 6 cm), can be attached to a lens adapter and then mounted on the standard 35 mm camera.
As mentioned above, the lens aperture control lever can be biased such that the aperture is normally at its maximum or minimum size. If a camera body that is designed to be used with a lens having its lens aperture control lever biased such that the aperture size is normally a maximum, is used with a lens having its lens aperture control lever biased such that its aperture size is normally a minimum, proper control of the aperture size cannot be achieved. Therefore, an auto exposure operation cannot be accomplished. This reduces the range of lenses that may be used with the camera body.